As a lithography technique in a semiconductor element manufacturing process, a double patterning technique by ArF-immersion exposure, EUV lithography, nanoimprinting and the like are known. A conventional lithography technique has held a variety of problems such as a cost increase and through-put deterioration, which have occurred with finer pattern processing.
Under such circumstances, application of directed self-assembly (DSA) to the lithography technique has been expected. Since DSA is generated by a voluntary behavior such as energy stabilization, a pattern with high dimensional accuracy can be formed. Especially, a technique of using microphase separation of a high-polymer block copolymer enables formation of periodic structures in a variety of shapes of several nm to several hundred nm by means of simple coating and an anneal process. The high-polymer block copolymer can be changed in shape to a spherical shape, a cylindrical shape, a lamella shape or the like in accordance with a composition ratio of blocks, and can be changed in size in accordance with a molecular weight, thereby forming a dot pattern, a hole or pillar pattern, line patterns or the like with a variety of dimensions.
Formation of a desired pattern in a broad range by use of DSA requires provision of a guide for controlling a generating location of a polymer phase formed by DSA. There are known as the guide a physical guide (grapho-epitaxy) that has a concavo-convex structure and forms a microphase separation pattern in its concave section, and a chemical guide (chemical-epitaxy) that is formed in a lower layer of the DSA material and controls, based on a difference in its surface energy, a forming location of the microphase separation pattern.
For example, a resist film is formed on a film to be processed, and a hole pattern to serve as the physical guide is formed in this resist film by photolithography. Coating of a block copolymer is applied so as to be embedded into the inside of the hole pattern, and then heated. This leads to microphase separation of the block copolymer into a first polymer section formed along a side wall of the hole pattern and a second polymer section formed in a midsection of the hole pattern. Subsequently, the second polymer section is selectively removed by irradiation with oxygen plasma, thereby to obtain a hole pattern reduced from the hole pattern formed in the resist film by photolithography. Then the film to be processed is processed using the resist film and the first polymer section as a mask.
However, when coating of the block copolymer is applied such that the block copolymer is appropriately embedded into the hole pattern, serving as the physical guide, in a region with a high pattern density of the hole pattern, the block copolymer is flooded from the hole pattern in a region with a low pattern density, and it has thus been not possible to obtain a desired microphase separation pattern. Conversely, when coating of the block copolymer is applied such that the block copolymer is appropriately embedded into the hole pattern in the region with a low pattern density, the block copolymer is not sufficiently embedded into the inside of the hole pattern in the region with a high pattern density, leading to formation of a microphase separation pattern with a small film thickness, and it has thus been not possible to obtain sufficient processing resistance.